[HH] CO detectors self-destruct

[Greg Rundlett (freephile)]

On Mon, Apr 17, 2017 at 1:33 PM, Tom Metro <tmetro+hhacking at gmail.com>
wrote:

> Federico Lucifredi wrote:
> > This excess life span I detected in use leads me to think the sensor
> > chemistry decays even when warehoused and not in powered use.
>
> Sure, that makes perfect sense given what we know about the sensors. The
> author of the teardown you referenced speculated that the limited
> lifespan was due to evaporation of the liquid and accumulation of
> contaminants in the activated carbon filter.
>
>
> > I think the lifespan runs from the date of manufacturing, and exceed
> > the warranty by an unknown amount...
>
> Yes, I assumed as much. As with any engineering parameter, the system
> should be designed with sufficient margin in excess of what is needed.
> And with a life safety device, even greater margins.
>
> But the issue at hand - with respect to having all your alarms die at
> once - is not the actual life of the sensor, but the duration of the EOL
> timer.
>

>From documentation that I found, the EOL timer is activated upon first
"power" - so installation by electrician if powered with battery backup, or
activation by consumer.  In my house, the detectors were all installed
during construction of the house.  They all died 6 years to the day from
the time they were installed.
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